Photometer.



c. LAYING.

PHOTOMETER. APPLICATION mEb JAN. 10 1916- 1,218,946. w Patented Mar.13,1917.

UNITED PATENT OFFICE.

CLAYTON LAING, OF CHICAGO, ILLINOIS.

PHOTOMETER.

Specification of Letters Patent.

Patented Mar. 13, 1917'.

Application filed January 10, 1916. Serial No. 71,187.

being had therein to the accompanying drawings.

In the art of photography, the subject of time exposure is an uncertainty. This invention relates to a photo-meter.embodying ,a constant or standard light and novel means for balancing or equalizing varied amounts of outside light with varied amounts of the standard light within the instrument, through a range of the intensity of lights from the lowest practical for photographic exposures to the brightest sunlight, to indicate in conjunction with previously determined calculation, the different periods of time required for exposures, for each of the several stops of a camera shutter.

A photometer in accordance with my invention embodies-a standard light adapted for comparison li ht a com )arator b which the intensit of two light rays may be compared, and novel cooperating shutters by which the intensity of the actinic elfect of the light rays may be measured to determine the proper duration of exposure for a sensitized photographic film or plate.

The comparator of the instrument includes two translucent members or blocks separated by an opaque screen or partition, and provision is made for facilitating close observation of said blocks. lVhen equal amounts of light penetrate the blocks they appear as one block, the two halves of the block perfectly balancing or showing that the light rays are of equal intensity. The standard or constant light of the instrument is preferably in the form of an incandescent lamp. ()rdinarily an electric light, when comparedwith sunlight, has an excess of rays from the rod end of the spectrum that makes it impossible to be properly balanced with sunlight. but in this instrument such inequality is eliminated by absorbing the excess red rays by means of a properly colored screen in front of the electric light.

The cooperating shutters of the instrument are of novel design and permit of a with an outside light or sun-' standard or known light and an unknown light being regulated in synchronism, until the actinical rays of the light harmonize or balance. lights of greater intensity than that from the standard and closing on the standard light for those of less intensity than that fromthe standard, a maximum illumination is obtained at the comparator, and this is accomplished by a single movement of the shutters. The difficulty in photometry for photographic purpose is the great range of intensity of light to be measured: exposures ranging in time from hundredths of a second to several minutes, which range an instrument must cover to be of value. The principle of cutting down an unknown light to balance with a standard light does not cover such range, because the standard light must be just strong enough to balance with the darkestunknown light practicable for photographic work. This isso weak that it is impossible to balance strong sunlight against it no matter how it is stepped down. The eye looking. from the bright sunlight could not perceive it, let alone balance it.

Cutting down on the standard light to balance with the outside light has the reverse disadvantage. The standard light being. so much weaker than the bright sunlight, it is necessary to set the comparator much farther from the unknown light in order to balance the sunlight, in which instance, the lights of weakerintensities are invisible; or,

by placing the comparator close enough to the unknown light in order to measure the weaker lights, the standard is not strong enough to balance sunlight. 1 l

The above difliculties in photometry have been obviated in my instrument by cooperating shutters whichalone cause the intensities of light rays to vary directly as the movement of the operating medium of the shutter, and with proper calibrations of the instrument, it is possible to accurately detern'iine time exposure for a photographic film or plate, consequently the several stops of a camera can be intelligently used in connection with my instrument to obtain a high degree of efiiciency in this branch of photography.

Reference will now be had to the drawing, wherein- Fi ure l is a longitudinal sectional view By closing on the unknown for .screwthreaded, as at v v the tubular casing 1 has an exteriorly screw of an instrument embodyin features of my invention;

Fig. 2 is'a side elevation. of the same; Fig. 3 is a-view of the outerend of the instrument;

taken on ceive the stationary outer shutters;

Fig. 10 is a yieyr of the outer end of the instrument casing, showing the stationary outer shutter in position;

Fig. 11 is a perspeetiveyiewof a rotary shutter member; and. I

Fig. 12 is an elevation of a detached comparator holder.

In describing my invention by aid or the views above referred to I desire to point out that the same are merely intended as illustrative of an example by which my in;

vention is applied in practice, and I do not care to limit myself to the precise construction and arrangement of parts shown. The following description is; therefore to be broadly construed as including substitute constructions and arrangement of parts which are the obvious equivalent of those hereinafter referred to.

. In the drawings, 1 denotes a tubular casing having the inner end thereof exteriorly threaded collar 3 and the bore of said collar is provided with a recess 4 as best shown in Fig. '9, to receive the tongue 5 of an outer stationary circular shutter 6 of less diameter than the bore of the collar 3 thereby providing a space or slot 7 between the collar and shutter When the latter is enounted in the former, as shown in Fig. l0 The outer sta tionary shutter 6 has a sector shaped opening 8 of ahoutfiO degreesradiating from the center of the shutter. The position'ofsth'e opening 8 relative to the shutter or casing 1 is in proximity to What may conveniently be termed the bottom. side of said casing.

Holding the outer stationary shutter (3 in engagement with thecollar 3 is an adjustable rotary shutter 9 provided with an annular, finger piece 10. The shutter 9 is held in parallelism with the shutter 6 by a retaining ring 11 screwed on the collar 3, and by removing said retaining rin and the shutters 6 and 9 easy access can be had to the interior of the casing 1. The shutter 9. as best shown in Fig. 3, has. anopening 12 The outer end hf by a closure 28 screwed or otherwise dot...

end Wall in the form of an involute curve starting at the center of the shutter and merging into the curved Wall of the opening.

The adjustable rotary shutter 9 has a recess l3 contigndus to the periphery thereof and in communication with the slot- 7 to receive a tongue la on the outer end of a cylindrical shutterconnecting member 15 rotatable in the casingl. The shutter connecting member 15, as best shown in Fig. 11, has acircumi erential slo't l6 providing clear; ance for a comparator to be hereinafter described, and the innerend of the member 15 terminates in a shutter 17 having an opening 180% similar shape to the opening 12 of the outer rotary shutter 9., but reversely disposed, as is apparent by comparing Figs. 3 and The outer end of the connecting member 13, being interlocked with the outer rotary shutter causes the shutters 9 and l? to move in synchronism when the finger piece 10 is rotated relative to the casing l, and the disposal of the openings 1:? and 18 isvery essential as will hereinafter appear.

The shutter 17 abuts and is in parallelism with a stationary inner shutter 19 carried by a sleeve 20 mounted in the casing 1.

The shutter 19 has a sector opening 21 corrcspending in size and shape to the opening 3 of the shutter 6 and the two openings long'l tudinally aline.

Engaging the end of the sleeve 20 a lamp holder 22 for an incandescent lamp 33, constituting a stationary or constant lig The holder 22 has contact means 2% for the terminal-25 of a suitable source of electrical energy, as a battery 26 mounted in a con tainer 27 ofinsulatio-n placed in the inner end of the casing 1. The battery and its container are retained within the casi ably mounted upon the inner end of said casing. and said closure has a resilient contact 29 for another terminal 30 of the bat tery. The resilient contact 29 constitutes a convenient switch by which an electrical circuit may be established through the casing l and the lamp holder 22 to the lamp 23 thereof. thus permitting of the lamp 2? being maintained as a light for a desired period of time.

Owing to the fact that the 'electric lamp 23, when illuminated, gives a larger percentage of red. rays than is present in sunlight it is impossible to properly balance the lamp rays against sunlight. A proper balance however. is obtained in this instru ment by absorbing the excess intensity or energy in the red end of the spectrum from the lamp by means of a suitably colored screen 31 placed over the opening 21 or the llO 'izo

Cit

' plate ll, similar to the screen 31, is placed over the opening 8 of the outer stationary shutter 6, as best shown in Fig. 1. These screens are very essential from a spectrum' standpoint in order that the intensities of light rays may be properly balanced tor observation purposes.

The comparator COlIlPIlSS an opaque flanged disk or partition 33 provided with a holder or cage 34 for blocks or pieces 35 and 36 of translucent material, as parafiin or milky glass. The blocks 35 and 36 are separated by an opaque partition or screen 37, preferably tinfoil, and these blocks are in longitudinal alinement .With the openings 8 and 21 of the stationary shutters 6 and 19 respectively. The holder or cage 34 has a socket member 38 for a magnifying ens 39 and the inner end of an eye piece 40, said eye piece being detachably mounted in an opening all provided therefor in the casing 1. The lens 39 obviates the necessity of a long eye piece and enlarges the edges of the blocks to the eye. The eye piece extends through-the circumferential slot 17 of the shutter connecting member 15 and constitutes a stop to limit the rotar movement of said member. been illustrated as having a funnel shaped outer end, but itis possible to make the outer end of the eye piece flush with the periphery of the casing to avoid any protuberance that might interfere with carry: ing the instrument. I

The periphery of the casing l, contiguous prising a comparator adapted to be simulto the collar 3, is calibrated as at -43 to correspond with similar stops or graduations of theshutter of the camera, and movable relative to said calibrations is a pointer or indicator 4'2 carried by the finger piece 10 and extending over the retaining ring 11. The first circumferential row of indicia positively determines photographic conditions relative to certain lights, and the remaining indicia is optional for the discretion of the operator.

In operation, the standard or constant light is established, the finger piece 10 Id-- justed, and the comparator observed. By

reason of the shape of the openings of the stationary shutters and the shape and disposal of the openings of the adjustabwshutters, the exposure area of the openings 8 and 21 may be independently decreased or increased by adjusting the finger piece 10.

Assuming that the intensity of light rays from the standard or constant light is The eye piece has greater than rays from the darkest outside light practicable for photographic work. and that the day on which a picture is to be taken is dark or cloudy, then the finger piece 10 is rotated clockwise to open the shutter 6 and gradually close the shutter 19, until the light rays of the two sources of light harmonize or balance in the blocks 35 and 36 of the comparator. With these two blocks appearing as one or harmonizing in shade or color the operator can observe tpe calibrations or indicia 43 indicated on t 1e casing l by the pointer 42 and set the shutter action :Q'f a camera in accordance therewith, thus assuring proper photo- "graphic exposure in connection with the lnewcd from time to time and the instrument maintained in operative condition. Should the battery Weaken and need renewing, such a condition can be readily detected in the comparator.

What I claim is 1. Means for comparing light rays, comprising a comparator adapted to beexposed to natural and artificial lights, and means for simultaneously varying the intensity of rays from said lights to balance the light intensity in said comparator.

2. Means for comparing light rays, comprising a stationary artificial light, a sta-- tionary comparator adapted to be exposed to said artificial light and to a natural light,

and shutters between said comparator and each light-movable in synchronism adapted for balancing the light rays in said comparator.

5. Means for comparing light rays, comprising a stationary artificial light, a com- .ficial light and to :1 natural to said aimiparator Led to be exposed ht, a shutter shutters.

7. A photometer comprising a. COTQPHIE" tor, means forzadmitting light rays various intensities to said comparator, and a 1 o tar member in the path of light i"; s at both sides of said comparator adapted For increasing and decreasing the intensity of said light rays until balanced in said comparator.

8. i photometercomprising a casing, a stationary light in an end thereof, a stationary comozu-ator intermediate the ends of said casing adapted to receive light rays from said stationary light and light rays from a natural source, and rotary means in said casing adapted to regulate the intensity of eithei'" light rays to balatu s the rays of light in said comparator.

9. A photometer comprising a casing, a

stationary light in an end" thereof, :1 stutionairy comparator interme into the ends of said casing adapter], to receive light rays from said .stational v light and ight rays from a natural source, shutters-between said comparator and said lights, and means connecting said shutters and operable at an end of said casing adapted to vary the intensity of the rays from said lights at said comparaon light, and

u itil said light rays are balanced in said comparator.

10. A photometer comprising a casing, it

shutter at one end thereof adapted to admit daylight to sold easmg, a comparator adjacent said shutter, a source of light detachbly mounted in theopposite end of said casa shutter in said casing between said .3m. mmtor and said source of light, and a in her counecting said shutters whereby said shuttersinay he'inoved in synchronism to balance light rays in said comparator.

11. In a. photometer, comparator exposed to two rays "nmslucent blocks in said cage adapted to independently reflect rays of light, and

means in the path of the rays of light adapted to move in syu'chronism to regulate the intensity of light rays in said comparator.

12. In a photometer, a comparator ex-. posed to rays of light, comprising a. cage, an eye piece in alinement with said cage, reflecting locks in said cage adapted to 3'8 fiect rays of light an opaque yartition between said blocks, and means in the path of the rays of light adapted to move in synchronism to regulate the intensities of light rays in saidcomparator.

13- A me lhod of comparing the intensities of light rays, consisting of simultaneously closing on one source of light and opening on the other source of light until the light rays balance atapoint predetermined to one source of light.

In testimony whereof I my signature in. the presence of a witness.

. v CLAYTUN LAENG.

Witness:

JANE ETHEL WHiTMAN.

of light, comprising a 

